FIG. 1 depicts a block diagram of telecommunications system 100 in the prior art. Telecommunications system 100 comprises: designating telecommunications terminal 101, designated telecommunications terminal 102, call-processing server 103, telecommunications network 104, telecommunications terminal 105, and telecommunications terminals 109 and 110, interconnected as shown.
Designating telecommunications terminal 101 is a personal computer (e.g., a laptop, etc.) that runs software that enables the terminal to provide telecommunications services to its user by transmitting and receiving packets of information. In this capacity, terminal 101 can be referred to as a softphone. Some of the telecommunications services that terminal 101 provides include placing and receiving calls, emailing, instant messaging, and so forth. Terminal 101 interacts with call-processing server 103 via a signaling channel to initiate a session to provide a telecommunications service. Terminal 101 uses the Session Initiation Protocol (or “SIP”) set of rules to initiate a session. Once a session has been initiated, terminal 101 transmits via telecommunications network 104 session-related traffic, such as voice or data, in packet format to one or more destinations, and also receives, via network 104, session-related traffic from one or more sources. Terminal 101 transmits and receives traffic by using the Internet Protocol set of rules and, as such, is an Internet Protocol-based terminal that is capable of providing Voice over Internet Protocol (or “VoIP”) to its user, among other services.
Designated telecommunications terminal 102 is a telecommunications terminal that is capable of exchanging information with call-processing server 103 for the purposes of transmitting or receiving voice or data traffic. Terminal 102 might be a packet-based terminal, similar to terminal 101, or it might be a circuit-based terminal based on older technology, such as a Plain Old Telephone Service (or “POTS”) wireline telephone. As part of a call or session, terminal 102 transmits and receives voice and data traffic via what is sometimes referred to as a media channel.
Telecommunications network 104 enables the transport of signaling information, as well as voice and data traffic, between the endpoints (e.g., terminal 101, call-processing server 103, etc.) in telecommunications system 100. Telecommunications network 104 might comprise one or more of the Public Switched Telephone Network, the Internet, one or more dedicated packet-based networks, and so forth. The Public Switched Telephone Network is a complex of telecommunications equipment that is owned and operated by different entities throughout the World. In the United States of America, for example, the Public Switched Telephone Network (or “PSTN”) comprises an address space that is defined by ten digits, and, therefore, comprises 10 billion unique addresses or “telephone numbers.” The Public Switched Telephone Networks in other countries are similar.
Call-processing server 103 is a private branch exchange that serves an enterprise network and is capable of exchanging signaling information and traffic with terminals 101 and 102. Call-processing server 103 is capable of switching incoming calls (e.g., from terminal 105, etc.) from telecommunications network 104 via one or more transmission lines to “on-premises” terminals 109 and 110. Call-processing server 103 is also capable of handling outgoing calls from terminals 109 and 110 to telecommunications network 104 via one or more transmission lines.
Call-processing server 103 is capable of also extending an incoming call (e.g., from terminal 105, etc.) to a telephone number of an “off-premises” terminal in telecommunications network 104, in addition to switching the same incoming call to an on-premises terminal within the enterprise area (e.g., an office building, etc.) that is served by server 103. Terminals 109 and 110 are considered to be on-premises terminals with respect to call-processing server 103, while terminal 102 is considered to be an off-premises terminal.
Call-processing server 103 exists in both the address space of telecommunications network 104 and the local address space of server 103's enterprise network, and acts as a “bridge” between the two address spaces. For example, when a calling party places a call to someone served by call-processing server 103, the calling party uses a dialing sequence that includes a telephone number that belongs to, and resides within the address space of, telecommunications network 104. As part of the dialing sequence, the calling party also uses an extension number that allows access to one of the on-premises telecommunications terminals that reside within enterprise-network (i.e., local) address space 112. Note that call-processing server 103 receives the extension number information either as digits that are dialed by the calling party separately from the telephone number or as part of the telephone number (e.g., the last four digits, etc.).
To accomplish the switching of an incoming, enterprise-related call to one of on-premises terminals 109 and 110, and the extending of the call to off-premises terminal 102, call-processing server 103 maintains a table that correlates (i.e., “links”) the off-premises telephone number to the on-premises, private branch exchange (PBX) extension. Table 1 depicts a table that illustrates the correlation.
TABLE 1PBX Extension-to-PSTN Number DatabaseOn-PremisesTelecommunicationsPrivate BranchTelecommunicationsTerminalExchange ExtensionNetwork Number109732-555-0102, x11201-555-1236110732-555-0102, x12908-555-3381. . .. . .. . .
As an example, a caller at terminal 105 who wishes to reach the PBX user of terminal 109 dials the PBX number (i.e., 732-555-0102). Call-processing server 103 receives the incoming call, including the extension number (i.e., ×11). Using information that is stored in memory and similar to what is shown in Table 1, call-processing server 103 determines that the call is also to be extended to off-premises telephone number 201-555-1236. The off-premises number corresponds to the off-premises terminal (e.g., a cellular phone, a home phone, etc.) that belongs to the PBX user of terminal 109, which is terminal 102 in this example. The idea behind transmitting the call to both terminal 109 and 102 is that if the PBX user is unreachable at his office phone (i.e., terminal 109), then he might be reachable at a phone that is outside of the office (i.e., terminal 102).
The softphone functionality of designating telecommunications terminal 101 enables its user to designate an endpoint in telecommunications system 100, such as designated telecommunications terminal 102, as having one or more privileges. One example of a privilege is handling all calls that are made to the user. The reason why a softphone user might want to designate a different terminal than the softphone to handle calls is because the other terminal, for example, (i) offers better quality, (ii) is functionally more capable, or (iii) has greater reliability than the user's laptop (i.e., terminal 101). To designate terminal 102 to be the recipient of calls, the user enters the address of terminal 102 (e.g., a telephone number, an Internet Protocol address, etc.) on his laptop, and the softphone application transmits the user request to call-processing server 103. Drawing on the earlier example, the PBX user that is associated with on-premises telecommunications terminal 109 would enter “201-555-1236” as the address of terminal 102 (i.e., the corresponding off-premises terminal that is being designated).